TIME-RESOLVED OPTICAL KERR-EFFECT MEASUREMENTS IN AQUEOUS IONIC-SOLUTIONS

We report the molecular dynamics of several solvated ions present in aqueous ionic solutions (HCl, HNO3, NaCl, and NaNO3) investigated by femtosecond time-resolved optical Kerr effect measurements. From the accurate fitting of decay curves, measured over 5-6 decades of intensity range, it has been possible to characterize (i) an instantaneous electronic response, (ii) a fast contribution of water, (iii) a rotational relaxation of the individual ions (tau(rot) similar to 2-3 ps), and (iv) a slow concentration-dependent decay connected to the direct ion-ion interactions. These results will be of interest to those seeking to measure electro-optic effects in aqueous solutions as these experiments give new information on the nature of the aqueous state.